Approximately 50% of the 700,000 individuals who survive a stroke each year have persistent upper extremity impairment. One reason why this percentage is so high is that the number of rehabilitative practice movements that they perform is too small. Ideally, individuals with a stroke would augment their clinical therapy by regularly attempting to use their impaired limb for functional activities throughout their day, yet this is currently not the case due to the greater effort required to use the impaired limb. As recently reviewed in JAMA, daily pedometer feedback has proven to be an effective way to increase walking activity for many individuals. Thus, the goal of this Phase II SBIR project is to develop and productize an interactive pedometer for the hand that will provide a similar benefit to people seeking upper extremity recovery after stroke. We have developed a first-of-its-kind magnetic sensor, the Manumeter, to wirelessly detect hand and arm movement in a socially acceptable and easy to don package. The user wears a small permanent magnet as a ring, and a sensing/logging wristband detects changes in the magnetic field as the ring moves; the wristband detects arm accelerations also. We have shown in initial studies that the Manumeter can accurately quantify amounts of functional activity. We thus hypothesize that people with a stroke who use the Manumeter to measure and motivate functional use of their upper extremity will improve their recovery. The aims of this Phase II grant are to: 1) Develop a production model of the Manumeter suitable for commercialization (months 1-24) by a) designing robust, scalable, and attractive hardware components; b) incorporating three novel interactive feedback functions; and c) partnering with a professional manufacturing firm to produce a commercial, FDA compliant version at scale. 2) Perform a usability study with individuals with a chronic stroke to make sure the device is easy to use and attractive (months 3-12). 3) Determine the effectiveness of interactive feedback from the Manumeter in improving upper extremity function in a pilot, randomized controlled trial with chronic stroke patients (months 12-24). In this study, eleven participants will use the Manumeter's interactive feedback functions to monitor and motivate upper extremity functional activity; eleven control participants will wear a Manumeter but receive no feedback and will be given the current standard-of-care for increasing upper extremity exercise, a book of home exercises. We hypothesize that the individuals who interactively monitor functional activity with the Manumeter will improve their upper extremity function significantly more as measured by the Box and Blocks score, ARAT, Motor Activity Log, Fugl-Meyer score, and Manumeter itself. This project will result in a commercially-ready, clinically-validated product that we will produce and sell.